@mixin u-prefix($property, $value, $prefixes: $saf-prefixes) {
    @each $prefix in $prefixes {
        @if $prefix == "webkit" {
            -webkit-#{$property}: #{$value};
        } @else if $prefix == "moz" {
            -moz-#{$property}: #{$value};
        } @else if $prefix == "o" {
            -o-#{$property}: #{$value};
        } @else if $prefix == "ms" {
            -ms-#{$property}: #{$value};
        } @else if $prefix == "spec" {
            #{$property}: #{$value};
        } @else {
            @warn "Unknown prefix: #{$prefix}";
        }
    }
}

@mixin u-prefix-all($value: true) {
    @if $value {
        $prefixes: ("webkit", "moz", "o", "ms", "spec");
    } @else {
        $prefixes: ("spec");
    }
}

@mixin u-prefix-only($only) {
    @if $only == "webkit" {
        $prefixes: ("webkit", "spec");
    } @else if $only == "moz" {
        $prefixes: ("moz", "spec");
    } @else if $only == "o" {
        $prefixes: ("o", "spec");
    } @else if $only == "ms" {
        $prefixes: ("ms", "spec");
    } @else {
        @warn "Unknown prefix: #{$only}";
    }
}